Sounds great. Don't know why you need a master valve, but can't hurt. I can picture you soaking disassembled emitter parts in vinegar and trying to srub off the deposits with a tooth brush. You would have to get inside the emitters to remove the calcium. Never had much luck with the vinegar methods, but maybe...
You mentioned catchement. Great idea, and totally removes hardness issues. However, has pressure issues. Since you only gain 0.43 PSI per foot of head, you might want to put a second set of PVC in that hard to dig ground when it is open, so you can easily shift form city water to the catchement, but leave both systems in place for dry spells. Other option is a small pump to raise the catchment water to a least 15 PSI after friction losses. It you plan to use gravity, You need to raise catvchment to supply at least 2 PSI at the beds. So with friction loss, the bottom of the tank needs to be at a minimum about 5 feet above you highest emitter. You certainly don't want to loose any more pressure with valves and pressure reducers, so I suggest one filter, and
manual full bore ball valves (Like 3/4 inch). They sell nice 1/4 turn brass ball valves (FPT to MHT) at L*wes for $8, or brass ball valve from numerous sources in MPT for about the same price. Full bore 3/4 inch means the opening is 3/4 inch in the ball when you look thru it.
A separate system, because it has special pressure needs and special emitters.
Useing 4 or 8 GPH emitters allows you to run as low as 2 PSI and get 1 GPH delivery. Tape systems (T-Tape, RhoDrip, AquaaTraxx) allow good row coverage, is cheap (although disposable into environment
), and operate on as low as 2 PSI.
Or, KISS and use a pump on the existing system. You seem like gadget guy, so may want to play with both ideas.
SO, put a second set of pipes in where you think you might need them. Bigger is always better, and 3/4 inch sch 40 PVC (don't use anything thinner wall if you are going to be digging in the area) @ 4 GPm = 240 GPH loses 1.42 PSI per 100 feet (plus more for fittings). So, not knowing distances, this is significant if yo are working with low PSI top start with. Using 1 inch sch 40 PVC, your loss at the same flow rate goes down to 0.44PSI/ 100 feet. So, even in low volume irrigation, at low pressure, bigger is better.
Finally, instead of using copper, you can use schedule 80 PVC above the ground. The concern is that PVC becomes brittle when exposed to sunlight. Copper does not. Copper, and it's fitings are expensive,asnd shoud be sweated rather than epoxy'ed. Also copper, is a real pressure killer, although in short sections probably not too much an issue. Stil the best for duration, lack of internal rusting, and appearance. PVC becomes brittle, but you can get at least 10 years out of schedule 40 in Texas sun. Longer with sch 80. Look for threaded pieces of Schedule 80 where the sell the risers for irrigaion, they are Grey. The brittleness issue is why PVC electrical conduit is gray colored, BTW, Black PE tubing used in drip has carbon black impregnated to make it
MORE UV resistant. Last longest if covered with mulch to shield it from your intense sunlight.
Sounds like you are having fun. Planning is alway a blast (which is one reason I do this). But from experience, ditch digging (especially in Texas Gumbo in the heat) is not so fun. Watch out for fire ants
Addenum. Flag emitters are good for gravity systems. So you can use them and maybe get away with one system. Electric valves eat pressure, and you need to make sure they will open at low pressure/flow rates. So, a master valve may not be a good idea. If you plan to use one pipe for everything, consider up sizing to 1 inch. In irrigation, "Bigger Is Better". eMail me for other ideas.
Jeff
This post has been edited 2 times, last edit by "Lowvolumejeff" (Aug 24th 2008, 1:04pm)